What factors limit fruit production in the lowbush blueberry, Vaccinium angustifolium? Melissa Fulton and Linley Jesson University of New Brunswick
Barriers to fruit production Pollinator abundance -specialists -generalists Pollinator behaviour -specialists -generalists Pollen quantity Pollen quality Pollen limitation Fruitset Genetics Disease Resources Nutrients
Lowbush blueberry Vaccinium angustifolium Specialist flower: Vibrate anthers to release pollen (buzz pollination) Linley Jesson Bumble bees buzz (specialist) Linley Jesson Honey bees cannot buzz (generalist) Duncan MacGillivray Leafcutters cannot buzz (generalist) Robyn Shortt Duncan MacGillivray Duncan MacGillivray All 3 bees are used as managed pollinators
Does pollen quantity limit reproduction (fruitset)? Do managed pollinators affect blueberry reproduction? If so, which pollinators? How do pollinators forage in blueberry fields and how might their behaviour affect fruit production?
Neguac 2010 & 2011 Bumblebees Leafcutters Honeybees & all combinations St. Stephen 2009 & 2010: Honeybees Pollen limitation Pollen deposition (Neguac 2010 & 2011)
Fruitset Clone shoots Pollen quantity Pollen quality - Open pollination - Supplemental pollen (outcross pollen)
Proportion Fruitset Open Supplemental mean +/- SE mean of all populations per region n=10 n=10 n=24 n=24
Does pollen quantity limit reproduction (fruitset)? yes Do managed pollinators affect blueberry reproduction? If so, which pollinators? How do pollinators forage in blueberry fields and how might their behaviour affect fruit production?
Pollen limitation not reduced by managed pollinators Neguac 2010 & 2011
stigmatic pollen load C control B bumble H honey L leafcutter & all combinations H p<0.05 HB p<0.05 Late season Early season Neguac 2010 & 2011 population
stigmatic pollen load C control B bumble H honey L leafcutter & all combinations H p<0.05 HB High p<0.05 pollen deposition But still pollen limited Late season Pollen Quality Early season Neguac 2010 & 2011 population
Count of honeybees per 20 min Count of Andrena per 20 min Weak effect of native pollinator abundance on fruitset
Does pollen quantity limit reproduction (fruitset)? yes Do managed pollinators affect blueberry reproduction? If so, which pollinators? very weak effect native pollinators How do pollinators forage in blueberry fields and how might their behaviour affect fruit production?
Flowers per inflorescence Tukey contrasts: Bombus - Apis = 0.6 Megachile - Apis <0.0001 Megachile - Bombus <0.0001 Visits: Honey 59/hour Bumble 89/hour Leafcutter 10/hour Honey bee Bumble bee Leafcutter bee
Does pollen quantity limit reproduction (fruitset)? yes Do managed pollinators affect blueberry reproduction? If so, which pollinators? very weak effect native pollinators How do pollinators forage in blueberry fields and how might their behaviour affect fruit production? most metrics of bee behaviour similar
Pollinator abundance -specialists -generalists Pollinator behaviour -specialists -generalists Pollen quantity Pollen quality Pollen limitation Fruitset Genetics Disease Resources Nutrients
Supplemental fruitset Regional variation indicates other factors p<0.00001 mean for each population (68 fields) St. Stephen 2009 St. Stephen 2010 Neguac 2010 Neguac 2011 Open fruitset
Supplemental fruitset Regional variation indicates other factors p<0.00001 mean for each population (68 fields) Disease Resource availability Native pollinator regimes Genetics - pollen viability, plant vigour St. Stephen 2009 St. Stephen 2010 Neguac 2010 Neguac 2011 Open fruitset
Significance of research Adding generalist pollinators : weak or no effect (on FS and PL) Adding specialist pollinators: no obvious effect (on FS and PL) Native pollinators having important contribution? Likely significant role of selfing in reducing fruitset Leafcutters Honeybees Robyn Shortt Bumblebees Duncan MacGillivray
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